The answer is "PET scan" or "PET-CT".
PET scan or positron emission tomography uses the technology behind conventional CT scans but performs to quantify the function in specific parts of organs (i.e. brain). The patient will be given a positron emitting substance most commonly fluorodeoxyglucose or FDG via intravenous injection. After which, the patient will go to the PET machine and the PET machine will measure the positron emitted throughout the body. Positron is well correlated to the function of a specific part of an organ.
